The present invention relates to a cleaning device incorporated in an image forming apparatus.
In a cleaning device for cleaning off a residual toner on a photosensitive member by upwardly directing a toner control face at a tip end of a cleaning blade to bring it into contact with the photosensitive member, Japanese Patent Publication No. 8-211797A discloses that the toner control face at the tip end of the cleaning blade is made inclined so that the toner may not be heaped on the tip end portion of the cleaning blade, thereby to prevent the toner heaped on the tip end of the cleaning blade from being scattered at the time of attaching and detaching the photosensitive member.
Japanese Patent Publication No. 2001-51522A discloses that a cleaning blade adapted to be contacted with and separated from an intermediate transferring member of a color image forming apparatus is provided in a cleaning device having a toner recovering chamber (a closed space), and the cleaning blade is brought into contact with the intermediate transferring member in an upwardly directed state thereby to clean off a residual toner.
In a case where the tip end of the cleaning blade has been brought into contact with an image carrier in an upwardly directed state as disclosed in the above publications, the toner is liable to be heaped on the tip end portion of the cleaning blade. Particularly, in a case where the toner recovering chamber is a closed space as disclosed in Japanese Patent Publication No. 2001-51522A, the toner is liable to be heaped on the tip end portion of the cleaning blade.
Even in a monochrome type apparatus in which the cleaning blade is kept in contact with the photosensitive member as in Japanese Patent Publication No. 8-211797A, there is anxiety that the toner which has been heaped on the tip end portion of the cleaning blade may fall down (be scattered) at the time of exchanging the photosensitive members.
In the case of the color image forming apparatus as disclosed in Japanese Patent Publication No. 2001-51522A, the cleaning blade must be separated from the image carrier after the cleaning has been finished, and there is arisen a phenomenon that when the cleaning blade is separated, the toner which has been slightly heaped on the tip end portion of the cleaning blade may fall down (be scattered), although in a very small amount. The motions of contacting and separating the cleaning blade with and from the image carrier are effected at every printing, and repeated in an order of ten thousand times or hundred thousand times during a lifetime of the image forming unit. Therefore, even though only a very small amount of the toner falls down per one contacting and separating motion, a considerably large amount of the toner will fall down In total.
Although it is conceived that a receiving tray may be provided for the solution of this problem, a large receiving tray must be prepared in order to afford a capacity enough to receive the fallen toner. This will incur upsizing of the apparatus, and goes against an intention of downsizing the apparatus. Moreover, a method of preventing the toner from being heaped on the tip end portion of the cleaning blade, by applying a bias voltage to the cleaning blade made of electrically conductive rubber to exert electrical force on an electrical charge of the toner has been also known. This method, however, is not appropriate for reducing the cost, because the cleaning blade of the electrically conductive rubber is expensive, and an electric source for applying the bias voltage must be prepared separately, which will incur an increase of the cost